Uremic leontiasis ossea due to secondary hyperparathyroidism complicated by vitamin C deficiency in a non-adherent chronic hemodialysis patient: A case report

Abstract

Non-adherence to medical therapy in patients with end-stage kidney disease (ESKD) can lead to severe metabolic derangements rarely seen in the current medical era. Such complications may take the form of secondary hyperparathyroidism (HPT) leading to rare manifestations of bone mineral disease, and profound vitamin C deficiency from poor nutrition combined with removal of water-soluble vitamins during dialysis. Secondary HPT causes renal osteodystrophy which can lead to diffuse enlargement of the facial skeleton and morphological changes suggestive of leontiasis ossea. We report a 36-year-old, non-adherent woman on chronic dialysis for over 10 years who developed progressive, diffuse facial bone enlargement in the context of years of extreme HPT and newly diagnosed severe vitamin C deficiency. Imaging revealed diffuse hypertrophy of the maxillary and mandibular bones. Histopathology showed extensive fibro-osseous proliferation without evidence of Brown tumor, suggestive of uremic leontiasis ossea. In this report, we discuss the orofacial manifestations of secondary HPT and the possible potentiating role of vitamin C deficiency on the development of renal osteodystrophy through altered vitamin D metabolism. Non-adherent patients on chronic dialysis should be evaluated for vitamin C deficiency, and the development of uremic leontiasis ossea should be considered when such patients present with distortion of facial features in the context of severe secondary HPT.

Keywords: end-stage kidney disease; hyperparathyroidism; leontiasis ossea; non-adherence; renal osteodystrophy; vitamin C deficiency.

Figure 1.. Facial morphology changes. Panels A and B are current photographs, whereas panel C is from 10 years earlier at start of dialysis.

Figure 2.. CT scan of the facial bones. The facial bones were enlarged, heterogeneous, sclerotic, and with some lytic areas, as well as bony expansion and tumefaction affecting most prominently the mandibular (left image) and maxillary areas, extending into the hard palate (right image).

Figure 3.. Role of vitamin C deficiency in vitamin D and PTH regulation. Vitamin C deficiency decreases 1-α-hydroxylase activity leading to decreased active vitamin D, which will in turn lead to greater transcription of PTH and less bone mineralization. Vitamin C deficiency also decreases the amount of vitamin D receptors (VDR) in the intestinal mucosal cells and the ability of active vitamin D to bind to the VDR in the intestine. This leads to a decrease in calcium absorption leading to hypocalcemia. Vitamin C deficiency may also blunt the activation of the calcium-sensing receptor (CaSR) by calcium, which could lead to higher levels of PTH. Finally, vitamin C deficiency may also lead to a decrease in collagen content of the bones through a decrease in hydroxyproline, a major constituent of bone collagen. Original figure produced by the study author DMA.